Experimental Study on Phase Change Material based Thermal Energy Storage System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1833
Experimental Study on Phase Change Material based Thermal Energy
Storage System
Anil C. Rathod1, Prof.C.V.Bandela2, Prof A.R.Rehman3
1 ME student, Department Of Mechanical Engineering, MGM’s COE, Nanded, Maharashtra, India.
2,3 Professor, Department Of Mechanical Engineering, MGM’s COE , Nanded, Maharashtra, India.
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Abstract - The use of phase change materials (PCM) is to
store the heat in the form of latent heat and sensible heat,
because large quantity of thermal energy is stored in smaller
volumes. In Our experimental investigation, calcium chloride
hexahydrate (CaCl2.6H2O) and sodiumcarbonatedecahydrate
(Na2CO3.10H2O) used as a Phase change materialand whichis
stored in copper tube and hot water is used as a heat transfer
fluid (HTF) that flows across the copper tube to charge and
discharge the phase change material storage system. The
experimental design is prepared by considering the
parameters: flow rate, heat transfer fluid inlet temperature,
PCM temperature, Heat stored, PCM meltingandsolidification
time (min). Experiments are conducted according to the
experimental design and responses are recorded. The effect of
selected parameters on TES using PCM is studied by analyzing
experimental data. Analyzing of these two PCM we have
calculated how much heat can be stored by PCM with respect
to above parameters.
Key Words: Phase change material [PCM] , salt hydrate,
TES, HTF, Latent heat storage capacity.
I. INTRODUCTION
Due to time-dependent and unpredictable characteristics of
sun exposure, utilization of solar thermal energy storage
tanks with phase change materials can be done to enhance
the performance of available solar water thermal systems.
Phase change material absorbs heat during its phase change
cycle from solid to liquid during the daytime solar cycle. The
amount of heat that a tank of water can absorb is much
higher with the presence of phase change material.
PCM is capable of storing and releasing large amounts of
heat energy. Heat is absorbed or released when the material
changes from solid to liquid and vice versa. PCM have the
capacity to store and release large amounts of energy, that
energy is called as latent heat. EachPCMhasspecific melting,
crystallization temperature and a specific heat storage
capacity. The analysis is carried out using two inorganic
phase change materials,suchas calciumchloridehexhydrate
(CaCl2.6H2O) and sodium carbonate decahydrate
(Na2CO3.10H2O).
A] Sensible heat storage system [SHS]:
Sensible heat storage system means the thermal
energy is stored by raising the temperature of a solid or
liquid. This system utilizes the heat capacity and the change
in temperature of the material during the process of
charging and discharging.
B] Latent heat storage system [LHS]:
A latent heat storage system based on heat
absorption or heat release when a storage material
undergoes a phase change from solid to liquid or liquid to
gas. However some practical difficulties also arise applying
the latent heat method due to low thermal conductivity,
density change sub cooling of the phase change materials
[3].The availability of solar energy is only during the day,
hence application required to store this energy as much as
heat is collected only the day time and this stored energy is
used during the night time. There are different ways in
which solar energy can be stored and one of the use is PCM.
The PCM is an effective way to store the solar energy. The
solar energy is free environmentally clean and therefore
used as a most promising alternative energy resources
option. The availability of total sunlight is seasonal and
depend on the metrological conditions of the location
(4).The present challenge is the storage of energy insuitable
form which can be conventionally converted into required
form. PCM is one of the most important methods for energy
storage system.
C] PCM (Phase change materials):
A phase change material is a substance with a high
heat of fusion, melting and solidifying at a certain
temperature. It has a capable of storing and releasing large
amount of energy. As compared to sensible heat storage
material PCM have maximum heat storage capacity (almost
5-14 times more heat per unit volume). The selection of the
PCM is totally based on a careful study of PCM properties of
the substance. Each PCM is not an ideal PCM. Theavailability
of PCM is also the factor to be considered. The total cost of
PCM is depending on the purity of the material. At this
particular time, a PCM become an important thermal energy
storing component and is beingunderuseinvariousthermal
storage devices such as in automobile sector and for
renewable energy applications. Due to their stability and

maximum heat storing capacity these materials are most
useful. In this paper two inorganic (salthydrate)PCM’swere
studied such as CaCl2.6H2O and Na2CO3.10H2O.
Table I: Thermophysical Properties of commercial
Grade CaCl2.6H2O and Na2CO3.10H2O.
II. METHODLOGY
Experiment set up:
Fig. 1 Experiment set up
Table II: Technical specifications of copper tube and
stainless steel:-
Sr.
No.
Tube Material Diameter
mm
Length
mm
Thickness
mm
1 Inner Copper 20 1080 1
2 Outer Stainless
steel
77 920 2
Procedure to carry out the testing-
1) Charging process :
In phase change material testing set up is used for
analysis of materials for their charging and discharging
process studied. For performance analysis first fill thewater
in both cold and hot water tank. Fill the required PCM in
copper tube. Then check the sensor position throughout the
points. Make sure the valves are properly adjusted for flow
purpose.
Firstly switch on the testing set up. Start the heater and
heat the water up to required temperature. Fill up the PCM
into the copper tube as per the volume. Start the pump and
adjust the flow rate for continues flow of water (Hot and
Cold). Pass the hot water from stainless tube for melting the
PCM which is present into the copper tube. PCM melts up to
the melting point in the form of latent heat in which the
temperature of storage material varies with the amount of
energy stored. Alternatively thermal energycanbestored as
a latent heat in which energy is stored when a substance
change from one phase to another by melting process. Take
out the readings as time in minute such as, 1) Hot water
temperature 2)Tube inlet water temperature 3) PCM
changing temperature 4) tube outlet water temperature, by
using the thermocouples. Measure the flow rates using the
flow meters provide to Hot as well as Cold water unit.
Continue the process till the material going to change its
phase from solid to liquid state. After getting highest
temperature stop the hot water flow and take out the
readings. Then start the cold water flow to convert liquid
PCM to solid PCM by discharging process.
2) Discharging process:
The discharging process was started withtheflowrateof 0.5
and 1lit/hr. The inlet temperature of cold water kept at the
atmospheric temperature that is 32°CorlowerthanthePCM
melting Temperature. During the discharging process the
cold water is circulated through over the copper tube.Now
the heat energy stored in PCM is transferred to the cold
water so the cold water temperature is increased
.temperature of the PCM and HTF are recorded at intervals
of 5 min. The discharging process is continued until thePCM
temperature reduces to atmospheric temperature. The
temperature of HTF at inlet and outlet are recorded.Alsothe
temperature of the PCM at two location are recorded. Like
that the flow rate changed to 1 lit/min and the PCM and HTF
temperature are recorded. The heat transfer fluid exit
temperature is time dependent because the rate of
solidification of the PCM varies with the time. This mode
terminates with the solidification of the PCM
Physical
Parameters
Phase Change Material
CaCl2.6H2O. Na2CO3.10H2O
Melting
point(°C )
29-30 32
Specific heat
(KJ/Kg°C)
Solid- 1.4
Liquid-2.1
Solid =1.88
Liquid=3.35
Latent heat of
Fusion (KJ/Kg)
190 267
Density (g/cm3
)
Solid =1.68
Liquid=1.80
Solid=1.44
Liquid=1.46

Fig.2: Line diagram of Experimental setup.
1. Hot water tank. 2. Cold water tank. 3. Pump. 4. Flow
meter. 5. Gate valve. 6. Copper tube. 7. Stainless steel tube. 8.
Power supply. 9. Temperature indicators.
III. Results and discussion
1) Charging process (Heat stored)
The charging starts with circulation of heat transfer fluid
heated in the collection system at a temperature higherthan
the PCM melting temperature. This Mode occurs during the
supply of hot water and heat energy stored up to the
complete melting of the PCM.
A] Charging effect on different flow rate for CaCl2.6H2O
as a PCM
Fig.3 illustrates the effect of varying the mass flow rate of
HTF (0.5 and 1lit/min) duringthecharging process.Increase
in mass flow rate has a small effect on the phase transition
process of PCM. As the flow rate is increased (0.5 to1
Lit/min) the heat storing as well as heat releasing capacity
increased.
Fig 3: Charging effect for Time Vs Temperature
B] Charging effect on different flow rate for
Na2CO3.10H2O as a PCM
Fig 4 illustrate the effect of varying the massflowrateof HTF
(0.5 and 1lit/min) during the charging process. Increase in
mass flow rate has a small effect on the phase transition
process of PCM. As the flow rate is increased (0.5 to1
lit/min) the heat storing as well as heat releasing capacity
increased.
Fig.4: charging effect for Time Vs Temperature
[2] Discharging process
Discharging temperature of CaCl2.6H2O
The discharging process is started by circulation of cool
water over the liquid PCM. The heat transfer fluid exit
temperature is time dependent because the rate of
solidification of the PCM varies with the time. This mode
terminates with solidification of the PCM.
A] Discharging effect of PCM on flow rate 0.5 lit/min for
CaCl2.6H2O
Fig 5 shows the outlet variation for CaCl2.6H2O and cold
water. The graph shows the cold water absorbs the heat
from the PCM Temperature and increased cold water heat
heat upto the 34°C.
Fig 5: Discharging effect for Time Vs Temperature

B] Discharging effect of PCM on flow rate 1lit/min for
CaCl2.6H2O
Fig 6 shows the outlet variation for CaCl2.6H2O and cold
from the PCM Temperatureandincreasedcoldwaterheatup
to the 34°C.
C] Discharging effect of PCM on flow rate 0.5lit/min for
Na2CO3.10H2O
Fig 7 shows the outlet variation for Na2CO3.10H2O and cold
to the 35°C.
D] Discharging effect of PCM on flow rate 1lit/min for
Na2CO3.10H2O
Fig 8 shows the outlet variation for Na2CO3.10H2O and cold
to the 36 °C.
[3]ComparisondischargingtemperatureGraphbetween
CaCl2.6H2O and Na2CO3.10H2O For flow Rate 0.5 lit/min
Fig.9 graphically compares the heat stored between the
CaCl2.6H2O and Na2CO3.10H2O when the flow rate is 0.5
Lit/min. It is observed that the heat stored in Na2CO3.10H2O
is higher than CaCl2.6H2O.when flow rate is increased the
heat storing as well as heat realizing capacity increased.
Fig.9: Comparison discharging temperature Graph
between CaCl2.6H2O and Na2CO3.10H2O For flow Rate
0.5 lit/min
[4]ComparisondischargingtemperatureGraphbetween
CaCl2.6H2O and Na2CO3.10H2O For flow Rate 1lit/min
Fig.10 graphically compares the heat stored between the
CaCl2.6H2O and Na2CO3.10H2O when the flow rate is 1
lit/min. It is observed that the heat stored in Na2CO3.10H2O
is higher than CaCl2.6H2O.when flow rate is increased the
heat storing as well as heat realizing capacity increased.

Fig10: Comparison discharging temperature Graph
between CaCl2.6H2O and Na2CO3.10H2O For flow Rate
1lit/min
[5] Thermal performance of the PCM System for
CaCl2.6H2O
Table 4 shows the performance of the CaCl2.6H2O with two
different flow rates. In this table energy released by the hot
water during charging mode (W) is 2267.1W at 0.5lit/min
and 4535.1w at 1lit/min. The Energy gained by the cold
water during discharging mode (W) is 1045.6 W at
0.5lit/min and 2232w at 1lit/min. The efficiency at 1lit/min
is 49.2% and the efficiency at 0.5 lit/min is 46.1% .In this
realized that when the flow rate is high the heat storing
capacity and efficiency is high.
Table 4: Thermal performance of the PCM System for
CaCl2.6H2O
Experiment no. I II
Flow rate during Charging mode 0.5
lit/min
1 lit/min
Flow rate during discharging
mode
0.5
lit/min
1 lit/min
Energy released by the hot water
during charging mode (W)
2267.1W 4535.1
W
Time interval during charging
mode (min)
5 Min 5 Min
Energy gained by the cold water
during discharging mode (W)
1045.6 W 2232 W
Time interval during discharging
mode (min)
5 Min 5 Min
Efficiency 46.1 % 49.2%
5] Thermal performance of the PCM System for
Na2CO3.10H2O
Table 5 shows the performance of the Na2CO3.10H2O with
two different flow rates. In this table energy released by the
hot water during charging mode (W) is 2267.1W at
0.5lit/min and 4535.1wat1lit/min.TheEnergygainedby the
cold water during discharging mode (W) is 1185.2 W at
0.5lit/min and 2927.9 W at 1 lit/min. The efficiency at 1
lit/min is 64.5% and the efficiency at 0.5 lit/min is 52%.In
this realized that when the flow rate is high the heat storing
capacity and efficiency is high.
Table 5: Thermal performance of the PCM System for
Na2CO3.10H2O
Experiment no. I II
Flow rate during Charging
mode
0.5
lit/min
1 lit/min
Flow rate during discharging
mode
0.5
lit/min
1 lit/min
Energy released by the hot
water during charging mode
(W)
2267.1W 4535.1
W
Time interval during
charging mode (min)
5 Min 5 Min
Energy gained by the cold
water during discharging
mode (W)
1185.2 W 2927.9W
Time interval during
discharging
mode (min)
20 Min 25 Min
Efficiency 52% 64.5%
IV. CONCLUSIONS
1) It is observed that the heat stored in 1lit/min is higher
than 0.5lit/min .so when flow rate is increased the heat
storing as well as heat releasing capacity increased.
2) When flow rate is higher the efficiency of the set up
increasing.
3) As per the performance in the Charging (heat storing)and
discharging processes, there is much difference between
PCM’s. But Na2CO3.10H2O performance is slightly better (5-
7%) than CaCl2.6H2O because of latent heat and specificheat
variation.
4) It means that Both PCMs are suitable for thermal energy
storage system but Na2CO3.10H2O is better than CaCl2.6H2O
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